1. Technical Field
The present invention relates to a method of forming a metal wiring and a method of manufacturing an active matrix substrate.
2. Related Art
As portable devices such as notebook PCs and cellular phones are becoming common, thin and lightweight liquid crystal display devices, etc. are becoming widely used.
In such liquid crystal display devices, etc., a liquid crystal layer is sandwiched between an upper substrate and a lower substrate.
An example of the lower substrate (active matrix substrate) is shown in FIG. 18.
As shown in FIG. 18, the lower substrate 1 includes a glass substrate 2, a gate scanning electrode 3, a source electrode 4, a drain electrode 5, a pixel electrode 6 (ITO), insulating layers 7, and a Thin Film Transistor 8 (TFT).
The gate scanning electrode 3 and the source electrode 4 are disposed such that one crosses over the other.
The drain electrode 5 is disposed also on the glass substrate 2.
The pixel electrode 6 (ITO) is connected to the drain electrode 5.
One insulating layer 7 is interposed between the gate scanning electrode 3 and the source electrode 4.
The TFT 8 is made of a thin film semiconductor.
In the formation of each metal wire on the lower substrate 1 above, a technique as disclosed in, for example, Japanese Patent No. 3261699 is used in which a step combining a dry process with a photolithography etching is repeated a plurality of times.
In this technique, however, there are problems in that the material costs and the maintenance fee tend to be increased and it is difficult to increase the yielding, since the step combining a dry process with a photolithography etching is repeated a plurality of times.
As a result, in recent years, there is a growing tendency of utilizing a liquid ejection system as a coating technique for use in the manufacturing process of electronic devices.
Generally, in a coating technique based on the liquid ejection system, a liquid substance is ejected as liquid drops from a plurality of nozzles provided in a liquid drop ejection head while a substrate and the liquid drop ejection head are relatively moved. The liquid drops are repeatedly deposited on the substrate to form a coating film.
The liquid drop ejection system has advantages such as in that the liquid substance is consumed with little waste and that the liquid substance can be directly applied in any pattern on the substrate without using a technique such as photolithography.
For example, in Japanese Unexamined Patent Application, First Publication No. H11-274671, Japanese Unexamined Patent Application, First Publication No. 2000-216330, Japanese Unexamined Patent Application, First Publication No. 2003-317610, etc., techniques are disclosed in which by ejecting a function liquid including a material for pattern formation from a liquid drop ejection head onto a substrate, the material is disposed (applied) on a pattern formation surface to form a fine wiring pattern of a semiconductor integrated circuit, etc.
The prior-art techniques as described above, however, have a problem such as described below.
For example, when a conductive layer of silver is formed by coating a glass substrate with silver nano ink according to the liquid drop ejection method, a foundation layer of manganese oxide, etc. is formed between the conductive layer and the glass substrate to improve a poor contact of silver with glass.
However, in the case in which the time from the applying to the baking of a silver nano ink is not managed and the glass substrate is baked after it is left standing for a given period of time, a void occurs in the silver at an interface with the manganese oxide. Thus, the degree of contact is decreased.